FAQ

Asbestosis is a type of pneumoconiosis that results from exposure to high levels of asbestos, developing into diffuse pulmonary fibrosis which begins at the peribronchiolar region.

Pathological changes in the pleura such as pleural plaque, diffuse pleural thickening, and hyperplasia of the visceral pleura that accompanies lung parenchyma with a band like shadow are useful in differentiating asbestosis from idiopathic interstitial pneumonia. However, there is more than a 5% chance that asbestosis will not combine with pleural plaque. There are cases in which calcified pleura plaque is present and even though there are findings of fibrosis in the lungs, they are not diagnosable asbestosis. Cases in which fibrosis is accompanied by chronic interstitial pneumonia or pulmonary emphysema are not uncommon, so it is important to obtain a detailed occupational history and ask if there was exposure to a high concentration of asbestos. In other words, we should take special note of pulmonary fibrosis with pleural plaque when the case is not asbestosis. The reason for this is that pleural plaque occurs even at exposure to low concentrations of asbestos, but also in many cases, it occurs in combination with asbestosis at exposure to high concentrations of asbestos. Therefore, the occurrence of pleural plaque is not a sufficient condition for the diagnosis of asbestosis.

Until some time ago, the definition of asbestos-related lung cancer was asbestosis complicated with primary lung cancer, and it was believed that fibrosis of the lung is important to the carcinogenesis mechanism. Recently, however, there have been asbestos-related lung cancer cases that were not complicated with asbestosis, and it is believed that asbestos itself is important for causing lung cancer.

Mesothelioma is a malignant tumor that originates from mesothelial cells or has the tendency to differentiate from the mesothelium, and occurs in the pleura, peritoneum, pericardium, or tunica vaginalis testis. Approximately 80% of mesothelioma cases originate in the pleura, and approximately 80% occur due to exposure to asbestos. Separately, SV40 virus, irradiation, and heredity have also been reported as other causes, but the frequency of these is low and lack consensus.

Among asbestos-related nonmalignant pleura lesions, inflammatory changes in the visceral pleura that accompany pleural effusions are called benign asbestos pleural effusions.

There are two types of pleural thickening due to asbestos: pleural plaque, which is a localized pleural thickening, and, diffuse pleural thickening. Diffuse pleural thickening is a visceral pleura lesion that spreads widely either unilaterally or bilaterally. The thickness ranges widely from less than 1 mm to more than 1 cm, and since the lesion reaches the parietal pleura, both pleura often adhere to each other.

By being exposed to asbestos, a flat and irregular protrusion is formed under the mesothelium of the parietal pleura and is accompanied by hyperplasia. Histopathologically, the cell components show scarce fibrous lesions. The most common sites for pleural plaque to originate are the anterior chest wall, the sixth to eighth dorsal costal cartilage, lateral thorax, side of the of vertebra body, and the upper bifurcation tracheae (Figures. 7 and 8). Also, calcification often occurs in the convexity of the diaphragm. On the other hand, it does not occur in the costo-diaphragmatic recess or the apex area.

Mesothelial cells primarily have a potential of differentiation to an epithelioid cell lined at the serosal surface as well as a mesenchymal-spindle cell presented under the serosal lining. Therefore, mesothelioma has many histological subtypes, including carcinoma-like (epithelioid) tumor or sarcoma-like tumor (sarcomatoid) tumor, or mixed epithelioid and sarcomatoid tumor.

Mesothelioma is a rare type of malignancy, which is highly related to asbestos exposure. Eighty to 90% of the patients with mesothelioma have a history of occupational and/or environmental exposure to asbestos. It is known that mesothelioma is a highly aggressive malignancy, and average survival of the patients has been reported to be only 13 months. The incidence of mesothelioma is lower to those of lung cancer, therefore clinicians as well as pathologists have fewer experience of diagnosis, especially at the earlier stage.